The object of the present invention is to provide a reusable window insulating system, which will not impose on the attributes of the existing window. At present, prior art which does not have a permanent mount to the existing window casing make use of light weight construction materials. The INTERIOR STORM WINDOW, by Thomas Sixsmith, U.S. Pat. No. 4,599,825 makes use of a thin acrylic glazing mounted in an extruded plastic frame. This design minimizes the weight on the flexible plastic sealing edge. The edge which is mounted on the perimeter of the frame holds the system in a vertical position within a window casing. In addition, the sealing edge may be affected by a window casing which is not smooth and/or horizontal. As noted by Sixsmith, a wedge addition may be needed to provide a better seal. The REMOVABLE WINDOW INSULATION SYSTEM, by Tamil D. Bauch, U.S. Pat. No. 4,485,990 makes use of a light weight foam insulating board. The weight of which will not compress the foam strip sealing edge. The foam edge which is mounted on the perimeter of the foam insulating board, holds the system in a vertical position within a window casing. The utility of said foam strip would be compromised if a heavier material were used in place of the foam insulating board. When inserted into a window casing, the nature of the material used in this system defeats the attributes of the existing window. Thus, the utility of existinq systems which have no permanent mounting is limited. The weight of material used in their construction being held in consideration with regard to the sealing edges.